In recent years, image forming apparatuses have been known that are capable of receiving not only an operation setting from an operation unit of the image forming apparatus, but also an operation setting from an external operation reception device such as a portable terminal. For example, there have been known image forming apparatuses that can detect a user's flick operation on a touch panel by a touch sensor or can simultaneously detect coordinates and loci of touch points of fingers by a multi-touch sensor. Such image forming apparatus can perform various operations according to a user's flick operation where a user's finger is swiftly moved on a touch panel or according to the number and loci of touch points, whereby the user's operability of the apparatus can be improved.
For example, a page information display device disclosed in PTL 1 enables the user to perform on an image a touch or flick operation that resembles a selecting or flipping operation on a physical medium (e.g. a sheet). It is therefore possible for the user to perform on a screen an intuitive image selection or flipping operation similar to an operation on a physical medium.